Implantable myocardial ischemia detection, indication and action technology

ABSTRACT

One embodiment enables detection of MI/I and emerging infarction in an implantable system. A plurality of devices may be used to gather and interpret data from within the heart, from the heart surface, and/or from the thoracic cavity. The apparatus may further alert the patient and/or communicate the condition to an external device or medical caregiver. Additionally, the implanted apparatus may initiate therapy of MI/I and emerging infarction.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/095,635, filed Aug. 7, 1998, entitled “Method andApparatus for In Vivo Detection of Myocardial Ischemia.”

FIELD OF INVENTION

[0002] The present invention relates to methods and apparatus fordetection and treatment of the disease process known as myocardialischemia and/or infarction (MI/I).

BACKGROUND

[0003] Ischemia occurs when the blood supply to the heart muscle istemporarily or permanently reduced, such as may result from theocclusion of a coronary artery. This occlusion may lead to localischemia or infarction of the heart muscle. Ischemia may also occur overlarge sections of the heart muscle due to conditions such as cardiacarrest, heart failure, or a variety of arrhythmias. The ischemic eventcan be of the so called “silent type” described in medical literature(e.g. not manifesting itself in terms of symptoms experience by thepatient or obvious external indications). The event can also be chronicwith continuously evolving symptoms and severity due to underlying heartdisease, or very abrupt and possibly even fatal due to infarction oflarge enough area of the heart to cause a large myocardial infarction.

[0004] The ischemic event often causes the performance of the heart tobe impaired and consequently manifests itself through changes in theelectrical (e.g. the electrocardiogram signal), functional (e.gpressure, flow, etc.) or metabolic (e.g. blood or tissue oxygen, pH,etc.) parameters of the cardiac function.

[0005] The conventional approach to detection of MI/I is to analyze theelectrocardiogram (ECG). An ischemic event results in changes in theelectrophysiological properties of the heart muscle that eventuallymanifest themselves as changes in the ECG signal. The current state ofthe art is to record these ECG signals from the body surface usingamplifiers and associated instrumentation. A standardized set ofelectrodes in an arrangement known as a 12-lead ECG has been developed.The conventional approach to the detection of ischemia and infarctionrelies on analysis and interpretation of characteristic features of theECG signal such as the ST-segment, the T-wave or the Q-wave.Computer-based technology has been employed to monitor, display, andsemi-automatically or automatically analyze the ischemic ECG changesdescribed above. The present technology includes ECG machines used indoctor's office, portable ECG machines known has Holter recorders,bedside monitors with displays, and sophisticated computer-based systemfor automatic analysis of the ECG signals.

[0006] Technology exists for providing therapy once ischemia isdetected. The most common approach involves thrombolytic therapy (byexternal infusion of drugs such as TPA or streptokinase) or opening ofthe blocked vessels using a variety of angioplasty catheter devices. Inthe event that ischemic condition results in malignant arrhythmia orarrest of the heart, an external defibrillator may be used to shock theheart and restore the cardiac rhythm.

[0007] Technology also exists for implanting therapeutic devices fortreating electrical conduction disturbances or arrhythmias of the heart.These devices include implantable pacemakers, cardioverters and atrialand ventricular defibrillators, drug infusion pumps as well as cardiacassist devices. The implantable devices typically use intracavitaryleads to sense the electrogram (EGM) and then provide electrical therapy(pacing or defibrillation) or mechanical therapy (pumping blood). Thesedevices sense the EGM and then utilize the features, such as improperconduction (in case of a pacemaker) or a fatal rhythm (in case of adefibrillator), or simply timing (to coordinate mechanical pumping).Notably, these devices do not specialize in the task of detecting,alerting the patient or treating ischemic heart disease.

[0008] Ischemia detection and analyses are usually done manually by theexpert cardiologist or by computers employing algorithms to detectischemia-related changes in the ECG signals. The preferred features ofthe ischemia detecting computer algorithms are the ST-segment and theT-wave. These features show elevation, depression or inversion of theseECG signals associated with ischemia. The computer then carries out acareful measurement of the degree of elevation/depression in a specificlead. By identifying ischemia dependent changes from specific leads, theischemic event is attributed to a specific region of the heart.

[0009] The current approach to diagnosis is that after an ischemic eventis perceived by the patient, they contact medical personnel such as the“911” system or their personal physician. Within the clinical setting,the patient is often monitored using a short recording of the ECG signalwhich may be interpreted by a physician. Alternately, the high riskpatient may be continuously monitored at the bedside in a cardiacintensive care unit. Therapy may include using drugs such as TPA, use ofcatheters for angioplasty (opening the blocked coronary vessel using aballoon or laser), or providing life support back up such asdefibrillation.

[0010] The aforementioned cardiovascular medical monitoring technologyand medical practice have several significant drawbacks in regard to thedetection and treatment of coronary ischemia which can result in severeconsequences to the patient up to and including death. They include thefollowing:

[0011] 1) Not being able to immediately alert the patient and/or thephysician of an ischemic event, particularly a life threatening event.

[0012] 2) Not being ambulatory with the patient; and/or an inability toprovide continuous monitoring to the patient and indication of thenecessary diagnostic information to the physician.

[0013] 3) Requiring input and interpretation of a physician or medicalpractitioner when one may not be present.

[0014] 4) Requiring monitoring devices external to the body, such as anECG monitor or external defibrillator, which are usually only availablein medical centers and hospitals, and which further need specialexpertise and attention from medical personnel.

[0015] 5) Reduced sensitivity or otherwise inability to detect ischemicevents due to loss of sensitivity from use of external electrodes.

[0016] 6) Loss of specificity as to the site of ischemia due toinadequate placement of electrodes in the vicinity of the ischemia orinfarction.

[0017] 7) Needing sophisticated expertise of a cardiologist to interpretthe clinical condition or needing monitoring instruments withsophisticated computer-aided ECG signal analysis capabilities.

[0018] 8) Over reliance on use of ECG signals for detection andinability to utilize and integrate other physiological data, (e,gpressure, blood flow, and PO2).

[0019] 9) Inability to immediately alert the patient or the physician ofthe impending or emerging ischemic condition.

[0020] 10) Inability to provide immediate treatment, particularly forlife-threatening events (e.g. myocardial infarction, cardiac arrest).

SUMMARY OF THE INVENTION

[0021] Certain embodiments of the present invention relate to methodsand devices for detection of myocardial ischemia and/or infarction(MI/I). Preferred embodiments relate to electrodes and sensors, devicesand methods for interpreting ischemic conditions, devices and methodsfor initiating the procedure to alert the patient and/or the care-giver,and devices and methods for connecting with a device that providestherapy. MI/I may be detected using implantable devices and methodsaccording to certain embodiments of the present invention.

[0022] Embodiments may include a stand alone device or a modification ofanother implantable device such as a pacemaker, cardioverter,defibrillator, drug delivery pump or an assist device. Embodiments mayuse a variety of in vivo sensors located inside the human torso and/orinside the heart. The sensor device preferably includes electrodes thatare indwelling in the heart, on or in the vicinity of the heart, underthe skin, under the musculature, implanted in the thoracic or abdominalcavity. Preferably the sensor device also includes strategic placementof the electrodes to capture the EGM signal from various positions andorientations with respect to the heart. The sensor device alsopreferably includes other hemodynamic or mechanical sensors that aresensitive to the condition of the heart in MI/I. MI/I may be recognizedusing analysis of the features of the signal, namely the EGM, recordedby the electrodes and sensors. The features of the EGM signal (namely,depolarization and repolarization), morphology, and analyticalinformation such as the spectrum, wavelet transform, time-frequencydistribution and others, are utilized in the interpretation andrecognition of the MI/I condition. Separately or in conjunction, thehemodynamic (namely, blood pO2, pH, conductance, etc.) and mechanicalparameters (blood pressure, blood flow, etc.) are sensed according tothe embodiments of this invention. MI/I is then recognized byintegrating some or all of the sensor information. Embodiments maydetect this MI/I event and alert the patient using a variety of methods,including but not limited to vibration, electrical stimulation, auditoryfeedback, and telemetry. The device to alert the patient may in certainembodiments be incorporated within the instrument itself. The patientmay be alerted by direct communication via electrical, sound, vibrationor other means or indirect communication to an external device in anelectromagnetic link with the implanted device. Once the MI/I event isidentified, the device may also institute therapy, such as infusion of athrombolytic agent or delivering life saving shock in case of an arrest,semi-automatically or automatically. The therapy giving device may beintegrated with the MI/I detection, MI/I analysis, and/or patientalerting device into an integrated or separate stand alone system.

[0023] Embodiments of the invention may be used to detect MI/I frominside the body as compared with the traditional approach of detectionby placing electrodes on the outer body surface of the torso. This ismade feasible in certain embodiments by using the MI/I detectiontechnology in an implantable device. Embodiments utilize sensors, suchas electrodes and leads, that record the EGM signal from inside thechest in the vicinity of the heart and/or from electrodes placed on theheart, and/or using catheters or leads placed inside the cavities (atriaand ventricles). Embodiments may include built-in interfaces toelectrodes, namely circuits for amplification and filtering of thesignals, and the circuit for digitization (analog-to-digital conversion)and processing (microprocessor). Embodiments of the implantable device,using its microprocessor, analyze the features of the EGM signal fromthese leads to detect an ischemic event.

[0024] Embodiments also relate to the design, construction and placementof electrode sensors. Embodiments may include an electrode lead withmultiple sensors capable of recording EGM from multiple, strategiclocations in the chest or in and around the heart. This embodiment alsoincludes utilization of the body of the instrument and single ormultiple leads.

[0025] Embodiments also relate to detection of the ischemic eventincluding identifying particular features of the EGM signal. Thesefeatures include depolarization (i.e. initial excitation of the heartwhen a beat is initiated, coincident with the body surface QRS complex)and repolarization (i.e. the subsequent repolarization of the heartcoincident with the body surface ST-segment and T-wave). MI/I results inalteration in depolarization and repolarization waves in selectedregions of the heart, for the case of focal ischemia, or the entireheart, for the case of global ischemia. These changes alter the actionpotential (of heart cells) as well as the conduction pattern (inselected regions or the whole heart). The alterations in actionpotential shape and conduction change together alter both thedepolarization features as well as the repolarization features).Depending on where an electrode is placed, these features may be seen indifferent recordings. The electrodes pick up the local signal (from theheart muscle in its vicinity) as well as the distal signal (distalmuscle areas as well as the whole heart). The characteristics of thissignal are identified in the form of shape changes, and these shapechanges can be identified in a variety of ways, including temporal,spectral, and combined approaches.

[0026] The MI/I detection technology according to embodiments of thepresent invention, may also utilize non-electrical measures, includinghemodynamic and mechanical parameters. An MI/I event may result in adegree of deprivation of oxygen to the heart muscle. This in turn mayresult in a decreased ability to perfuse the heart muscle as well as thebody. This may result in a cyclical reduction in the mechanicalperformance in terms of contractility and pumping action of the heart.Sensors placed inside the blood stream pick up the changes in bloodoxygen, pH, conductance, etc. resulting from the MI/I event. The MI/Ievent would lead to small changes in case of mild ischemia or infarct orsignificant changes in case of global ischemia or cardiac arrest. Thesensors are usually placed inside a catheter or a lead, although sometimes in the body of the instrument, and then measurements may be madevia the electronic circuit interfaces inside the implantable device. Themechanical function of the heart may be detected utilizing sensors andleads, including those for pressure, volume, movement, contractility,and flow.

[0027] Embodiments also relate to methods and devices for signaling thehost patient or others (such as medical personnel) to the incidence ofMI/I. When MI/I is detected, it is imperative to take therapeuticactions rapidly and even immediately. Thus, the patient needs to beinformed and the caregiver physician needs to be informed. Embodimentsof the invention include devices and methods for communication betweenthe implantable device and the host/physician. One of these approachesis to use radio-frequency or radiotelemetry, while another is tocommunicate through electrical stimulation. Other approaches, includingsound, and magnetic fields are also devised. Embodiments may alsoutilize long distance, remote and wireless means of communication usingtelephone, telemetry, Internet and other communication schemes.Embodiments may also include the code of communication by which theinformation pertinent to MI/I is presented in detail. This code may beeither analog or digital, relayed via the communication link, and thendecoded by the receiving instrument or individual. The code primarilysignals to the host patient, or the external device attached to thepatient, or directly to the medical caregiver, the condition of MI/I.The code may include information about EGM, the MI/I condition, andother related diagnostic information. The code may also includerecommendation and instructions to provide an immediate therapy to thepatient to treat MI/I.

[0028] Another aspect of certain embodiments of the invention includescoupling of the MI/I detection technology to a variety of therapeuticdevices. The implantable MI/I detection technology makes it feasible torapidly initiate therapy through direct access to the body, circulatorysystem or the heart. In some circumstances it is desirable to infusedrug such as Streptokinase or TPA to treat the patient. Other drugs mayalso be infused immediately or subsequently on a steady state basis. Inother instances it is desirable to carry out procedures such asangioplasty. In case the MI/I event leads to a life-threateningarrhythmia or cardiac arrest, means to treat the arrhythmias toresuscitate the heart are disclosed. These may include use of electricalpacing, cardioversion and/or defibrillation. In case the MI/I eventleads to a failure of the heart, means to assist the heart aredisclosed. These assistive devices include left or right ventricularassistive device and artificial heart pump. Embodiments may declareinterface of the implantable myocardial ischemia detection technology tothese therapeutic approaches and the use of these therapies upondiscovery of MI/I by the implanted devices.

[0029] Another aspect of certain embodiments of the invention includesthe use of the technology in an implantable device. The implantabledevice may include a hermetically sealed can, electronics, analog anddigital logic, microprocessor, power source, leads and sensors, circuitsand devices to alert the patient, communication link and interface tothe external diagnostic and therapeutic means. Embodiments also includemodification of implantable arrhythmia detection devices, pacemakers,defibrillators, infusion pumps, or assist devices to have the novelfeatures described above. The technology used in embodiments of thepresent invention can be partially or fully integrated into theseinstruments. Embodiments further include hardware, software or firmwaremodification of the aforementioned devices to have MI/I detection,alerting and therapy initiating features.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Certain embodiments of the invention are described with referenceto the accompanying drawings which, for illustrative purposes, are notnecessarily drawn to scale.

[0031]FIG. 1 illustrates a schematic illustration of the torso and heartwhich also includes the implantable device, its sensing lead, an alarmmeans, a therapy device, and a communication means to an external deviceaccording to an embodiment of the present invention.

[0032]FIG. 2: (a) illustrates a preferred embodiment including animplanted device such as a pacemaker with a full 12-leadelectrocardiographic configuration (L, R, F and V1 through V6, andground reference) using an implantable intra-cavitary and intrathoraciclead; (b) illustrates a second preferred embodiment using an implanteddevice and a single suitably positioned intrathoracic lead with multiplesensors in the chest and the ventricular cavity of the heart; and (c)illustrates a third preferred embodiment with a suitably placed devicewith multiple electrical contact sensors on the implanted device can anda suitably threaded lead through the thoracic, abdominal and theventricular cavity along with the sensor means.

[0033]FIG. 3 illustrates a preferred embodiment, such as acardioverter-defibrillator with suitable sensing or shocking lead withsensor means indwelling the heart and ventricular cavity and a series ofsensors on the shocking lead on the epicardium or the thoracic,abdominal and ventricular cavity.

[0034]FIG. 4 illustrates three of the many placements and shapes of theimplanted device inside the thoracic or abdominal cavity, and the sensormeans on each can of the implanted device with each sensor insulatedfrom the can (see the inset), according to embodiments of the presentinvention.

[0035]FIG. 5 illustrates three preferred embodiments with suitableimplanted device in the thoracic cavity, placement of differentelectrode leads and sensors and their different configurations withrespect to the heart. The sensor configuration includes leads with (a)unipolar, (b) bipolar sensing and (c) physiologic sensor means insidethe ventricular cavity of the heart.

[0036]FIG. 6 illustrates the (a) electronics and microprocessor systemused in the implantable myocardial ischemia detection device, and (b)the circuit diagram for amplification and filtering of the EGM signal,according to embodiments of the present invention.

[0037]FIG. 7 illustrates (a) the depolarization and repolarizationsignals of the electrocardiogram, the action potential, normal andischemic EGM, the pressure signals, and time-frequency responsecharacteristics of the EGM, (b) the electrical activation pattern on theheart as visualized by isochronal conduction distribution in normallyconducting and ischemic zones.

[0038]FIG. 8(a) illustrates various communication links between theimplantable device and the external monitoring devices, includingalerting the subject with the aide of a loud speaker, vibrator orelectrical stimulation, communication to and external device via RFcommunication, audio communication, and magnetic field modulationaccording to embodiments of the present invention.

[0039]FIG. 8(b) illustrates the implantable MI/I detection technologypiggy-backed or incorporated as a part of a modified implantablepacemaker or a cardioverter-defibrillator according to embodiments ofthe present invention.

DETAILED DESCRIPTION

[0040] Certain embodiments of the invention pertain to methods anddevices for detecting ischemia or infarction, diagnosing, alerting thepatient and/or treating the ischemic heart disease.

[0041] Implantable myocardial ischemia and/or infarction (MI/I)detection technology according to certain preferred embodiments isillustrated in FIG. 1. Embodiments include methods and devices to detectand treat MI/I. One embodiment of a method includes: i)placement/implantation of the device inside the chest or other bodycavity, ii) placement and implantation of electrodes and sensors toselected areas of the myocardium, iii) connection of one or more of theelectrodes and sensors to the implanted device, iv) detection of anischemic event by the analysis of the EGM signal and sensor data, v) themethod of analysis of the EGM signal using signal processing means intime and frequency domain, vi) communicating the stored EGM signals toan external device using telecommunication means, vii) alerting thepatient of the event, vi) communication with the medical attendant usingtelecommunication means, and vii) initiating or implementing medicaltherapy for MI/I. Embodiments may include some or all of the aboveelements, which are described in more detail below.

[0042] One preferred embodiment is illustrated in FIG. 1. It includes aplurality of devices (101) and sensors (102) that are implanted in thehuman body (103). Referring to FIG. 1, this implementation may includeone or more of the following steps: i) a device that would reside insidethe body (103) and alert the patient (106) or the medical attendant ofan impending or ongoing ischemic event and undertake therapeutic action,ii) one or more implanted sensors (102) positioned in selected areas ofthe heart (104), such as a ventricular cavity (105), and connected tothe aforementioned device, iii) detecting an ischemic event, iv)alerting the patient of the event as depicted in (106), v)communication, as depicted in (107) with a device external to the body(108) or a medical attendant, vi) administration of medical therapy viaan intracavitary pacing electrode (109), infusion of drug through thebody of the lead (102) or shocking the heart between leads (102 and110).

[0043] Another preferred embodiment of the device and its method of useis illustrated by FIG. 2(a). The device (101) is implanted in thethoracic cavity under the skin or muscle in the vicinity of the heart(104). The sensing may be accomplished by a detailedelectrocardiographic system that provides a device for biopotentialrecording from locations around the heart that result in a more completeassessment of the ischemic regions of the heart. The leads arepositioned in one or more configurations within the chest to form aninternal Einthoven's triangle (an external Einthoven's triangle is aconcept known in the art). This configuration provides the advantage ofenhanced signal sensitivity for discrete selectable areas of themyocardium and allows for easy determination of particular cardiacvectors. The resultant 12-lead electrocardiographic system is employedby those skilled in the art on (not internal to) the chest to provideprojection of the cardiac dipole at various electric field orientations.A cardiologist or a computer program is then employed to determine thesite and degree of MI/I by interpretation of the electrocardiogram. Inthe present invention, an intra-thoracic lead system is designed torecord the EGM activity using a plurality of sensors situated to recordprojections of the cardiac dipole from inside the body in a manneranalogous to the Einthoven's triangle and a 12-lead recording systemfrom outside the chest. A lead (201) system comprises a biocompatibleinsulated carrier device with a plurality of electrically conductingmetallic sensors that conduct the EGM signal from in or around the chestto the circuitry within the implanted device. The lead depicted in FIG.2 carries three sensors (202, 203, 204) corresponding respectively tothe left arm (L), the right arm (R) and the foot (F) projections of the12-lead system. A Wilson's central terminal, a central terminal derivedthrough a resistive network, is provided to derive the leads I, II, IIIand the three augmented leads (external, but not internal, Wilson'scentral terminal and leads are concepts known to the art). The lead isattached to the body of the implanted, hermetically sealed device (101)via a connector (205) that provides a feed-through interface to thecircuitry within. Another lead (206) carries additional sensors (207through 212) corresponding respectively to the V1 through V6 projectionsof the 12-lead electrocardiographic system. The body of the device or aconducting sensor incorporated there in provides the ground or thecircuit common reference G (213). The sensor signals are electricallyconnected via the lead to the circuitry within the implanted device. TheEGM signals recorded from this lead system is analyzed for the featuresof MI/I.

[0044] Another preferred embodiment shown in FIG. 2.2(b) comprises animplanted device (221) in the abdominal or lower thoracic cavity (220)with a preferred lead system (222) with a plurality of sensors. The leadsystem (222) makes a connection through a feed-through connector (223)to the circuitry of the implanted device (221). The lead (222) issuitably implanted within the thoracic cavity and in and around theheart (105) to place the sensors at locations that allow recordingsanalogous to the aforementioned 12-lead electrocardiographic system. Thedesign involves the placement of the conducting sensors so that theirplacement inside the thoracic areas of the body (103) and in and aroundthe heart (104,105) preferably corresponds to the 12-leadelectrocardiographic system. Thus, the sensors V1 through V6 and L, R,and F (224) along with the ground reference G on the body of the device(225) represents all the electrodes needed to reconstruct the fullelectrocardiographic system, comprising leads I, II, III, augmentedleads, and chest leads, suitable for implantable technology. The EGMsignals from this lead system (222) may then be analyzed for theindications of MI/I.

[0045] Another embodiment is depicted in FIG. 2(c). An implanted device(230) is located in the lower thoracic or abdominal cavity and a lead(231) with sensors therein is threaded through the intra-thoracic areasof the body (103) and in and around the heart (104,105). The leadcarries the sensors L, R and F, while the body of the implanted devicecarries the sensors V1 through V6, wherein the sensor array shown as(232). The body of the device (230) carries the ground or the circuitcommon G, while the conductive sensor elements shown as the open circlesare insulated from the body of the device as shown by the dark ringsaround the circular sensor body (233). This lead system suitablycaptures the EGM signals from the various regions of the body which arethen electrically conducted by the lead (231) to the implanted device(230).

[0046] Still another embodiment is illustrated in FIG. 3. An implanteddevice (101) placed inside the body (103), utilizes a plurality of leads(301) and (306) and sensors therein. The lead (301) carries with it thesensors L, R and F for EGM sensing within and around the heart (104,105). The lead 301 also carries plurality of sensors (302) formechanical or hemodynamic information from within the ventricular cavity(105). The lead (306) connects sensor element (307) carrying pluralityof sensor V1 through V6 (308). The body of the device (101) carries theground reference G.

[0047] In yet another embodiment of the present invention, an implanteddevice is placed inside the chest in the proximity to the heart. Thedevice is shaped in a manner so that it can carry on its case one ormore leads (electrodes and their combination) suitable for recordingmultiple EGM signals. There are several locations that are preferred.FIG. 4 shows the thoracic part of the body (103), the heart (104), andthree of the suggested locations and shapes of the device (401, 402,403), each one of these locations and electrode placements is to be usedindependently and exclusively. These locations allow preferredorientation of the electrodes and leads for detection of EGM signal. Forexample, location (401) with three electrodes (405, 406, 407) givepreferred orientation of the ECG in conventional left arm and lead Ibetween (405, 406) signal from the cardiac dipole. The three sensorsalso give other projections from the heart when taken in pairs (406,407) and (405, 407). The body of the can or an additional metal sensorinsulated from the can is used as a ground reference. Alternately, thesignals from the sensors (405, 406, 407) may be summed using resistivenetwork, known, in external devices but not implanted devices, asWilson's central terminal, to provide a common or reference signal. Thelocation (403) analogously has 3 electrodes (408, 409, 410) which givethe conventional right arm and lead I between (408, 409) signal, andother differential pairs II and III between (409, 410) and (408, 410).The location (403) has sensors V1 through V6 (411) giving 6 chest leadsignals. In all these designs and placements the sensors are mounted onthe encasement of the device known as the can and hence do not requireseparate leads or wires going out from the can via the feed-through tothe heart or to the body. The can and the associated sensors can beentirely hermetically sealed and contained in a single case. The can maybe made of a biocompatible material including, but not limited tostainless steel, titanium or a biocompatible engineered polymer such aspolysulfone or polycarbonate and the like. The inset in FIG. 4 shows theelectrical sensor element (406) surrounded by insulating ring (407)mounted on the can (403). The conducting sensor element provideselectrical connection to the circuitry inside the can of the implanteddevice. The electrical sensor or the body of the implanted device servesas the ground or the circuit common reference. While three preferredembodiments are illustrated, the exact location of the implanted deviceand the electrical sensor elements can be varied to provide sensing andthe lead oriented to improve the sensitivity to detection of the MI/Ifrom a particular region of the heart. For example, a can at location(401) would pick up left and superior infarcts, a can at location (402)would pick up right and superior infarct, and a can at location (403)would pick up left or right inferior infarcts. In addition, in certainembodiments the container or can may be eliminated or integrated intoone of the other components.

[0048] In a preferred embodiment of the device, an intracavitaryindwelling lead system, as depicted in FIG. 5, is used to sense the EGMsignals. Referring to FIG. 5(a), the implanted device (101) encases inthe can the electronics while the body of the can serves as the groundor the reference G or otherwise a sensor on the lead serves as theground or the reference (501). The intracavitary lead consists of a lead(502) going from the device (101) into the right ventricular cavity viathe venous blood vessel by the methods well known in the art. The lead(502) may be preferentially threaded through the right or the leftsubclavian veins. The lead (502) may also be threaded through inferiorvena cava or IVC. The lead (502) is placed in the atrial or theventricular cavity or both. The lead (502) also may lodge in the SVC andthrough the septal region in the left ventricular cavity. The lead (502)may be placed in the left ventricle via the arterial vessel. The leadmade of biocompatible material including, but not limited topolyurethane or silicon carries within it the metallic coil or wire forproper insertion of the lead (502). The lead (502) carries at its tipthe pacing electrode (503) by which electrical stimulation is deliveredto the heart muscle. Although depicted in this figure as being incontact with the ventricular muscle, the pacing electrode (503) may alsobe in contacting with atrial muscle or other suitable pacing regions onthe heart surface. The sensing and the pacing electrodes may be designedinto a single lead body or separate lead bodies. The atrial andventricular chambers of the heart may be sensed and paced separately orjointly. The external body of the lead also carries the conductingsensor element such as (504) to contact and capture electrical signalfrom the cavity of the heart (105). A plurality of electricallyconducting contact points (505) on the lead serve as sensor elements. Asthese sensor elements (504) span the atrium to the ventricle, typicallyon the right side of the heart, these sensor elements (504) capture theEGM signal associated with that part of the heart. In the preferredembodiment in FIG. 5(a), the sensor elements are arranged in theunipolar configuration wherein the sensor elements are well separatedfrom one another, each capable of capturing electrical signal withrespect to the ground reference G on the body of the can or electrode(501). In another preferred embodiment illustrated in FIG. 5(b), thesensor elements are arranged in a bipolar configuration wherein pairs ofsensor elements (506, 507) are closely spaced. A plurality of sensorelement pairs (508) are arranged in the region spanning the atrium,ventricle or both. In another preferred embodiment, illustrated in FIG.5(c), the sensor element can be at or close the tip of the catheter(510) and may include one or more of many hemodynamic sensors (e.g.pressure, pO2, pH, temperature, conductivity, etc.) or mechanicalsensors (strain gauge, accelerometer, etc.).

[0049] Preferably the implanted device consists of a casing or a canmade of biocompatible and hermetically sealed case consistent with longterm implantation in the hostile environment of the body (with its warmtemperature, humidity, blood, etc.). The can is shaped in a variety offorms illustrated in FIG. 2 and FIG. 3. The circuitry associated withthe sensor is housed inside this can and may be driven by battery power,typically one of the many contemporary pacemaker/defibrillator batteriesusing lithium or lithium ion or polymer battery technology well known inthe art. The internal circuitry may utilize ultra-low power analog anddigital circuit components built from miniaturized packages and runningoff the battery power supply. One overall schematic design isillustrated in FIG. 6(a) and consists of the input protection stage(601) which serves to protect the amplifier from possible shock hazards.This front-end should also meet electrical safety and leakagespecifications conforming to safety standards as set by AAMI, AmericanHeart Association and other standard setting bodies. This stage isfollowed by the amplifier (602) and followed by electrical isolationcircuitry (603), if necessary. Isolation can be electrical or optical.The isolation circuit is followed by the output stage (604) which feedsall the analog signals from multiple channels into a multiplexer, MUX(605). The multiplexed signal is digitized using an A/D converter(analog to digital converter) (606) and then fed into a microprocessor(607). The principal circuit component is the EGM amplifier, which isdesigned using operational amplifiers as illustrated in FIG. 6(b). Theamplifier circuitry consists of protection (610) and filtering (611)components (including diodes, capacitors and inductive chokes),operational amplifier based instrumentation amplifier (612), and activecircuit filters for band-pass filtering (613). In various embodiments,the hardware implementation may use a low power, low voltagemicroprocessor or a custom-designed ASIC or a fully custom VLSI circuit.In an alternative embodiment, the hardware would be contained, orotherwise piggy-backed onto an implantable pacemaker orcardioverter-defibrillator. In this case the ischemia detectiontechnology would use information derived from the existing leads of theimplanted pacemaker or defibrillator. Also, the detection software wouldbe embedded in the RAM or the ROM and executed by the microprocessor ofthe implanted pacemaker or cardioverter-defibrillator.

[0050] The sensors of the implanted device are preferably configured tocapture the EGM signal and other physiologic data. From these signalsand data, algorithms implemented by the microprocessor and its softwareidentify the ischemic event. Embodiments utilize the EGM signals frominside the body using a plurality of sensors placed inside the thoraxand in and around the heart. The sensors preferably seek to mimic theinternal or implanted form of the Einthoven triangle and the 12 leadelectrocardiographic system. The complete 12 lead system may not alwaysbe used and the MI/I event can be captured from only a limited set ofleads and electrodes. The complete or partial set of these sensors, soarranged, provide a projected view of the heart's dipole at varioussensor locations. The signals recorded from a sensor then give anindication of the MI/I event in its vicinity and the recorded pattern isindicative of the degree of severity of the MI/I event. Certainembodiments utilize both depolarization and repolarization signalcomponents of the EGM signal to detect ischemia events. As illustratedin FIG. 7, ECG signal (701) is accompanied by the action potentialsignal (702), the EGM signal (703) and the pressure signal (704). UnderMI/I conditions, these respective signals may be modified as shown in(705, 706, 707 and 708). Note the appearance of notches in the QRScomplex and depression of the ST-segment (705 and 710). Correspondingly,the action potential (706) shows change in upstroke (713), duration andshape (714). Consequently, the EGM signal shows fractionation andmultiple depolarization and changed shape (707). The ventricularpressure signal shows a reduction in magnitude as well as shape change(708). The ischemic conditions are some times localized to parts of theheart (focal ischemia or infarct) and at other times throughout theheart (global). Ischemia results in slowed conduction and possiblefractionation of the conduction patterns. FIG. 7(b) illustrates theconduction on the heart (750) in normal conditions (left), with traces(752) showing isochronal lines t1 through t6 (places receivingsimultaneous activation). An infarcted is indicated as a region 751 onthe heart with no isochronal lines, and consequently it is a regionwhich alters the conduction pattern. Therefore, under ischemicconditions (right), the conduction pattern (752) is altered as indicatedby the isochornes t1 through t10. The isochrones show differentpathways, indicating dispersion and fractionation of conduction. Thisdispersion and fractionation of conduction produces the EGM signaldepicted for ischemic hearts (707) and its features thereof (716).

[0051] The EGM signal for normal versus ischemic myocardial tissue canbe distinguished using a variety of means including waveform analysisdone in both the temporal and frequency domain and combination of both,which is called a time-frequency method. FIG. 7(a) graphicallyillustrates the EGM signal for a healthy heart (703) with a relativelylarge major peak and related inflection and transition pointscorresponding to depolarization and repolorization events occurringduring the cardiac cycle (702). In contrast, the ischemic signal shownin (707) shows significantly more peaks and has unusual transitionalpoints (716). This phenomenon is known as fragmentation and is readilydistinguishable. An alternate approach is to detect ischemia in thefrequency domain. FIG. 7 also illustrates the time-frequency analysis ofthe EGM signal. The EGM signal is analyzed through Fourier analysiswhich is well known in the art and its frequency components are thusobtained. Since the EGM signal is time-varying, time-frequency analysisis more suitable so as to obtain instantaneous frequencies at differenttimes in the cardiac cycle. Magnitude of signal power, indicated byhorizontal lines at various frequencies (717) and plotted versus time(718) is calculated. In this case, the ischemic EGM time-frequencydistribution (719) is distinguished from the time-frequency distributionof the healthy EGM waveform (720) by a broader range of frequencies atone or more depolarization, repolarization and fractionation eventlocations. Further during repolarization, there is shift towards lowerfrequencies corresponding to the ST-segment elevation or depression andT-wave morphology changes in the ECG. Several different approaches oftime-frequency and time-scale analyses are applicable to calculatinglocalized frequency information at various instants of the EGM signals.Normal and ischemic EGM waveforms/signals are thus distinguished and theelectrodes or sensors displaying the characteristic changes identifyischemia in their vicinity. This approach is extended to analysis ofsignals from various sensors. FIG. 7(a) shows the cavitary pressuresignal in normal (704) and ischemic (707) hearts. Analogously, acavitary probe measuring conductance can obtain an estimate of theventricular volume by methods well known in the art. The magnitude andmorphology of the conductance signal is also indicative of MI/I.Analogously, ventricular volume signal assessed by the aforementionedconductance method also identifies local changes in the conductance andproportionately the volume in the region of the ventricular cavity.Therefore, a comparison of such signals placed in different positions inthe heart (e.g. 505, 508, 509), allows estimation of ventricular volumesat different points in the cardiac cycle and at different locations inheart. Information from the EGM signals (electrical conduction) andhemodynamic/mechanical signals (conductance, pressure, ventricularvolume, blood volume, velocity etc.), may be used separately or combinedby one or more algorithms, programmable devices or modified pacemaker,cardioverter, defibrillator systems seeking to detect an ischemic event.Ischemic diagnostic function may be further enhanced by combininganalysis of ECG and hemodymanic data with metabolic/chemical data (e.g.PO2, CO2, pH, CK (creatine kinase)) collected using in dwelling sensorswhich may be chemical FETs, optical fibers or otherwise polarimetric oroptical based, and the like, all well known in the art.

[0052] In another embodiment of the ischemia detection sensors, a use ismade of the multiple sensors spanning the lead in the ventricularcavity. The sensors (505 or 508 or 509) in FIG. 5 capture the changes inthe EGM signals in their vicinity. An analysis of the relativemorphologies would help identify the ischemia in the vicinity of theelectrode. The electrode sensors record the EGM signals whose morphologyor frequency characteristics in normal or MI/I conditions is similarlyanalyzed by the methods illustrated in FIG. 7(a). The EGM signalrecorded and analyzed results from spontaneous heart beats or from pacedbeats. Spontaneous heart beats are produced by the heart's own naturalrhythm. Paced beats are produced by a pacing electrode usually at thetip of the lead placed in the atrial or the ventricular cavity. Themorphology and the frequency characteristics of the paced beats areanalyzed for MI/I condition.

[0053] Once an incident of MI/I is detected, the patient or the medicalcare giver needs to be informed so that quick intervention may be taken.Noting that certain aspects of embodiments relate to an implanteddevice, the device needs to communicate the signal out to the patientand/or the physician. FIG. 1 provided a scheme for the communicationbetween the implanted device (101) and the subject (103) or the externaldevice (108). Now, for further detail, FIG. 8 illustrates an implanteddevice (801) comprising its amplifier and data-acquisition system (802)and microprocessor (803) communicates data and message to the subject orthe external device via a D/A converter (804), a parallel port (805), aserial port (806 or 807). The D/A converter is connected to an amplifier(808) which drives a loud speaker, buzzer or a vibrator (811). Theexternal device may receive this information via a microphone (815). Thesubject may preferably receive the alert message via audio or vibratorysignal (811). Alternately, the subject may receive the indication of anMI/I via an electrical stimulus feedback delivered via a voltage tocurrent converter, V-I (829) delivered to the case of the implanteddevice or to a stimulating lead. The serial port communicates theelectrical signals via a modem (809), and a transmitter (812) to anantenna (815) for radio frequency or audio telemetry to the externaldevice. The external device receives the radio telemetry communicationvia an antenna (816) and a receiver (817) and subsequently conveys thesedata to a computer connected to the receiver. Alternately, the implanteddevice may use a serial port (807), connected to a modem (810) and atransmitting coil capable of generating and receiving magnetic fields(818). By pulsed or alternating magnetic field, a message pertaining tothe MI/I event or digitized data from the microprocessor (803) arerelayed to the external device. An external coil capable of generatingor receiving magnetic field communicates the message to and from theimplanted device (819) via magnetic induction. The magnetic fieldfluctuations are processed and a message or data stream may becommunicated to a computer connected to the external device. These areamong many alternative means to enable communication between theimplanted device and the external device may be operated/worn by thephysician or the patient. Other communication technologies well known inthe art may also be utilized. The implanted and the external deviceengage in a unidirectional (sending the MI/I alert or sending actualdigital or analog data over the link) or bidirectional (external devicesending commands, internal sending the data, for example).

[0054] Certain embodiments also include devices and methods for taking atherapeutic action. The therapeutic action is possible because implanteddevice provides an early indication of an event of MI/I. Therefore,there may be adequate time for this system to perform therapeuticactions to prevent or minimize the development of an infarction. Invarious embodiments of the invention, therapeutic actions may comprise:infusion of thrombolytic agents such as TPA and streptokinase oranticoagulant agents such as heparin. Since it is known that there istreatment window of several hours after infarction which can preventmore serious medical complications, a timely bolus or steady release ofthese medicines may prevent or otherwise ameliorate the conditions thatmay be precipitating the MI/I. FIG. 8(b) illustrates the schema in whichthe implanted device (801) equipped with a lead (833) connected to asensing means (831) initiates the action of transmitting a message via atransmitter (832) in a manner described previously. It also initiatesinfusion of any of the aforementioned drugs via an infusion line or acatheter (835). For example, the drug may be in the catheter tip itselfembedded in a slow release polymeric matrix whose release is actuated bythe implanted device. Alternately, the drug may be in the device itselfand released via infusion tubing (835). The acute MI/I may precipitate alife-threatening arrhythmia. In case such an event, involvingarrhythmias such as ventricular tachycardia or fibrillation, theimplanted device may initiate electrical rescue therapy, such as pacing,cardioversion or defibrillation. An electrical shock may be given viatwo leads, which may be a combination of the can of the implanted device(801) and an intracavitary lead (833) or a combination of subcutaneousor an epicardial or intrathoracic lead (834) and an intracavitary lead.Thus, the implanted device would initiate the therapeutic proceduressemi-automatically by first alerting the patient or automatically viainfusion of a drug or delivery of electrical rescue shock.

[0055] While aspects of the present invention have been described withreference to the aforementioned applications, this description ofvarious embodiments and methods shall not be construed in a limitingsense. The aforementioned is presented for purposes of illustration anddescription. It shall be understood that all aspects of the inventionare not limited to the specific depictions, configurations or relativeproportions set forth herein which may depend upon a variety ofconditions and variables. The specification is not intended to beexhaustive or to limit the invention to the precise forms disclosedherein. Various modifications and changes in form and detail of theparticular embodiments of the disclosed invention, as well as othervariations of the invention, will be apparent to a person skilled in theart upon reference to the present disclosure. For example, the logic toperform various analyses as discussed above and recited in the claimsmay be implemented using a variety of techniques and devices, includingsoftware under microprocessor control or embedded in microcode, orimplemented using hard wired logic.

[0056] While the invention described above presents some of thepreferred embodiments, it is to be understood that the invention in notlimited to the disclosed embodiment but rather covers variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A method comprising: monitoring the heart forevidence of myocardial ischemia/infarction (MI/I) using a deviceimplanted into a subject; alerting the subject upon detection of MI/Iusing a signal generated by the implanted device and transmitted to thesubject.
 2. A method as in claim 1, wherein the detecting MI/Icomprises: sensing an electrogram signal; determining the occurrence ofMI/I based on the electrogram signal.
 3. A method as in claim 1, whereinthe detecting MI/I comprises: positioning a plurality of leads andsensors in the subject; transmitting data from the sensors to amicroprocessor; and determining whether an MI/I event has occurred.
 4. Amethod as in claim 3, wherein the alerting the subject comprises sendingthe signal to a device external of the subject.
 5. A method as in claim1, further comprising sending a signal to a device external of thesubject.
 6. A method as in claim 1, further comprising initiatingtherapy within the subject after detecting MI/I.
 7. A method as in claim1, further comprising providing a supply of a medicine as part of thedevice implanted into the subject and supplying a dose of the medicineto the subject after detecting MI/I.
 8. A method for monitoring theheart of a subject for MI/I inside of the subject, comprising:implanting into a subject's chest a container including circuitry and amicroprocessor; providing a plurality of sensors electrically connectedto the circuitry; positioning at least one sensor in or on the heart ofthe subject; and determining whether MI/I has occurred.
 9. A method asin claim 8, wherein the plurality of sensors includes at least onesensor from a group consisting of electrical, mechanical and hemodynamicsensors.
 10. A method as in claim 9, wherein the microprocessor includesat least one algorithm for interpreting a signal generated by the atleast one sensor and determining whether MI/I has occurred.
 11. A methodas in claim 9, wherein the container is implanted subcutaneaously.
 12. Amethod as in claim 9, wherein the container is implanted withintracavitory connections.
 13. A method as in claim 9, wherein thecontainer is implanted with epicardial connections.
 14. A method as inclaim 9, wherein the container is implanted with electrical access to aplurality of chambers of the heart.
 15. A method as in claim 9, whereinthe container is fully implanted within the blood vessels and cavity ofthe heart.
 16. A method as in claim 9, wherein the container isimplanted with access to intracavitary blood.
 17. A method as in claim9, wherein the container is implanted with access to intravascularblood.
 18. A method as in claim 8, wherein at least one sensor ismounted on the container.
 19. A method as in claim 8, wherein thesensors are attached to leads extending from the container, the methodfurther comprising positioning leads at three orthogonal locations onthe container.
 20. A method as in claim 8, wherein the sensors arepositioned in a configuration selected from the group consisting oforthogonal, Einthoven triangle, and chest lead configuration.
 21. Amethod as in claim 3, wherein the positioning a plurality of leadscomprises positioning the leads in an Einthoven triangle placement. 22.A method as in claim 3, wherein the positioning a plurality of leadscomprises positioning the leads so that the sensors are configured in anorthogonal pattern.
 23. A method as in claim 3, wherein the positioninga plurality of leads comprises placing the leads to form sensingconfigurations in a plurality of regions in the heart that enhancesensitivity to MI/I.
 24. A method for monitoring a heart in a subjectfor evidence of MI/I comprising: implanting a container includingcircuitry and a microprocessor in the subject; and providing a pluralityof leads extending from the container, wherein at least one lead extendsto a position inside of the heart.
 25. A method as in claim 24, furthercomprising positioning a plurality of leads in a plurality of heartchambers.
 26. A method as in claim 24, further comprising positioning aplurality of leads to provide electrical access to a plurality ofchambers of the heart.
 27. A method as in claim 24, further comprisingpositioning routing at least one lead inside a heart cavity selectedfrom the group consisting of the atrial and the ventricular.
 28. Amethod as in claim 24, further comprising positioning at least one leadto provide electrical access to epicardial regions of the heart.
 29. Amethod as in claim 24, further comprising positioning at least one leadto provide electrical access to thoracic regions surrounding the heart.30. A method as in claim 24, further comprising positioning at least onelead to provide electrical access to subcutaneous regions adjacent inthe vicinity of the heart.
 31. A method as in claim 24, furthercomprising positioning multiple electrically conductive sensor elementson at least one lead.
 32. A method as in claim 24, further comprisingpositioning multiple sensor elements selected from the group consistingof unipolar elements and bipolar elements on at least one lead.
 33. Amethod as in claim 24, further comprising mounting at least one sensorelement on the container.
 34. A method as in claim 24, furthercomprising: transmitting at least one signal through at least one of theleads to the circuitry; amplifying the signal; filtering the signal; andconverting the signal from an analog signal to a digital signal.
 35. Amethod as in claim 34, wherein a plurality of signals are transmittedthrough a plurality of leads and are delivered to the circuitry, furthercomprising feeding the signals to a multiplexer, converting the signalfrom an analog signal to a digital signal, and delivering the signal tothe microprocessor.
 36. A method as in claim 1, wherein the detectingmyocardial ischemia comprises: using at least one sensor selected fromthe group consisting of a cavitary pressure sensor, a myocardialcavitary volume sensor, a blood pO2 sensor, a blood pH sensor, a bloodlactate sensor, and a tissue impedance sensor; wherein the sensorcomprises a portion of the device implanted into the subject; andwherein the sensor is capable of distinguishing a myocardial ischemiacondition from a non-myocardial ischemia condition.
 37. A method as inclaim 36, wherein at least one sensor comprises a myocardial cavitaryvolume sensor that operates using conductance.
 38. A method as in claim1, wherein the detecting myocardial ischemia includes separating anormal from an ischemic electrogram signal, the method comprisinganalyzing the electrogram signal using an analysis selected from thegroup consisting of (1) an electrogram waveform analysis for temporalfeatures, (2) an electrogram waveform analysis using time-domain signalanalysis methods, (3) an electrogram waveform analysis using a frequencydomain method such as FFT and filtering, and (4) an electrogram waveformanalysis using a combined time and frequency analysis method.
 39. Amethod as in claim 38, wherein the analyzing the electrogram signalcomprises using an electrogram waveform analysis for at least onetemporal feature selected from the group consisting of peaks andinflections.
 40. A method as in claim 38, wherein the analyzing theelectrogram signal comprises using a frequency domain method selectedfrom the group consisting of fast Fourier transform and filtering.
 41. Amethod as in claim 38, wherein the analyzing the electrogram signalcomprises using a combined time and frequency analysis selected from thegroup consisting of joint time frequency distributions and waveletanalysis.
 42. A method as in claim 1, wherein the alerting signalcomprises a signal selected from the group consisting of an electricalsignal, a magnetic signal, an electromagnetic signal, and an auditorysignal.
 43. A method as in claim 1, wherein the device comprises aportion of an implanted apparatus selected from the group consisting ofa pacemaker, a cardioverter, a defibrillator, a cardiac assist device,and an infusion pump.
 44. A method for monitoring electrogram signals,comprising sensing changes in depolarization resulting from MI/I.
 45. Amethod as in claim 44, further comprising sensing changes inrepolarization resulting from MI/I.
 46. A method for monitoringelectrogram signals, comprising sensing changes in combineddepolarization and repolarization and determining whether a MI/I hasoccurred.
 47. A method of detecting a myocardial ischemia signal in asubject, comprising analyzing an electrogram signal by determining itstemporal features synchronous to the Q, R, S, and T waves in a surfaceECG signal.
 48. A method as in claim 47, wherein determining itstemporal features synchronous to the Q, R, S, and T waves includesproviding a plurality of leads for delivering signals to a deviceimplanted in the subject, storing an electrogram signal morphology fromeach lead into a digital memory, and comparing the stored electrogrammorphology to the stored electrogram signal.
 49. A method as in claim48, wherein the analyzing includes: identifying changes in themorphology of depolarization upstroke synchronous with the Q and Rwaves; identifying changes in the morphology of depolarizationdownstroke synchronous with the R and S waves; and identifying changesin the morphology of repolarization synchronous with the S and T waves.50. A method as in claim 49, further comprising obtaining theelectrogram signal from at least one lead positioned in a locationselected from the group consisting of endocardial, pericardial, thoraciccavity, subpectorial and subcutaneous.
 51. A method as in claim 50,wherein the analyzing comprises analyzing a unipolar electrogram signal.52. A method as in claim 50, wherein the analyzing comprises analyzing abipolar electrogram signal.
 53. A method as in claim 24, furthercomprising a plurality of sensors coupled to the plurality of leads, anddetecting the location of a MI/I site by sensing signals from sensorslocated at different positions within the subject and analyzing thechanges in the signal at the different positions.
 54. A method as inclaim 53, wherein the analyzing comprises calculation of cardiac dipolesof the MI/I site by dipole projection.
 55. A method as in claim 53,wherein a plurality of the leads are positioned orthogonal to eachother.
 56. A method as in claim 53, wherein the detecting the locationis determined using leads selected from the group consisting oforthogonal leads, Einthoven triangle leads, chest leads, and endocardialcavitary leads.
 57. A method for distinguishing normal and ischemicsensor information comprising analyzing temporal and spectral sensorsignals derived from a plurality of sensors implanted in a subject. 58.A method as in claim 57, further comprising detecting MI/I using aplurality of sensors selected from the group consisting of pressuresensors, volume sensors, conductance sensors, impedance sensors, pHsensors, pO2 sensors, temperature sensors, and blood-based biochemicalsensors.
 59. A method for monitoring a subject for MI/I, wherein apacemaker is connected to the subject's heart, the method comprising:analyzing a paced electrogram signal; monitoring MI/I related to changesduring a depolarization event in the paced electrogram signal; andmonitoring MI/I related to changes during a repolarization event in thepaced electrogram signal.
 60. A method as in claim 59, wherein thepacemaker is positioned at a location selected from the group consistingof atrially, ventrically and dual chambered.
 61. A method for reading,storing and relaying information from an apparatus implanted in asubject, the information being relating to a MI/I event in the subject,the method comprising: providing a plurality of analog signals relatingto the myocardial event to circuitry connected to a analog to digitalconverter controlled by a microprocessor implanted in a subject;converting the analog signals to digital data; storing the digital datain a memory of the microprocessor; recording the digital data into acontinuous loop in the memory and overwriting old data therein;recovering stored MI/I information; and transmitting the stored MI/Iinformation to an external device as an electromagnetic code.
 62. Amethod as in claim 61, further comprising displaying the electromagneticcode on the external device and analyzing the displayed electromagneticcode.
 63. A method as in claim 1, wherein the alerting the subject iscarried out by electrical stimulation of the subject.
 64. A method as inclaim 1, wherein the alerting the subject is carried out by acommunication selected from the group consisting of auditorycommunication and vibratory communication.
 65. A method as in claim 1,wherein the alerting the subject is carried out using an electromagneticlink to an external device worn by the subject.
 66. A method as in claim1, wherein alerting the subject is carried out by activating a deviceselected from the group consisting of an external pager and externalalarm.
 67. A method as in claim 1, further comprising alerting a personother than the subject upon detection of a MI/I using a method selectedfrom the group consisting of electrical communication via RF links,modulation of a magnetic field signal, electromagnetic transmission,auditory transmission, digital encoding and transmission of a signal,and analog modulation and transmission of a signal.
 68. A method as inclaim 8, further comprising communicating between the implantedcontainer and a device external to the subject, comprising positioningthe external device adjacent to the torso of the subject.
 69. A methodas in claim 8, further comprising communicating between the implantedcontainer and a device external to the subject.
 70. A method as in claim69, wherein a modem protocol is used to communication between theimplanted container and a telephone.
 71. A method as in claim 8, furthercomprising communicating between the implanted container and a deviceexternal to the subject, wherein the communicating is carried out usingradiotelemetry.
 72. A method as in claim 8, further comprisingcommunicating between the implanted container and a device external tothe subject, wherein the communicating is carried out using linksbetween the implanted container and a computer system.
 73. A method asin claim 8, further comprising communicating between the implantedcontainer and a device external to the subject, wherein thecommunicating is carried out using links between the implanted containerand a healthcare provider's computer system.
 74. A method as in claim69, wherein the device external to the subject comprises a deviceselected from the group consisting of a telephone and a pager.
 75. Amethod as in claim 8, further comprising communicating between theimplanted container and a device external to the subject, wherein thedevice external to the subject includes an emergency care network.
 76. Amethod for treating a subject comprising: implanting a device in thesubject; detecting MI/I using the device; initiating a therapy in thesubject based on a signal generated by the device.
 77. A method as inclaim 76, wherein the therapy comprises delivering at least one drugselected from the group consisting of bicarbonate, epinephrine, heparin,TPA, streptokinase, and beta blockers.
 78. A method as in claim 76,wherein the at least one drug comprises an anti-arrhythmic drug.
 79. Amethod as in claim 76, wherein the device includes at least one drugembedded in a polymer matrix and initiating therapy includes the releaseof the drug through the polymer matrix.
 80. A method as in claim 76,wherein the device includes at least one drug embedded in a portion ofthe device selected from a lead, a catheter and tubing, and initiatingtherapy includes releasing a drug from the portion of the device.
 81. Amethod as in claim 76, wherein initiating the therapy includesdelivering an electrical shock to the subject.
 82. A method as in claim76, wherein the therapy is initiated immediately after detecting MI/I.83. A method as in claim 76, wherein the therapy includes treatment thatcan be carried out by the implanted device.
 84. A method as in claim 83,wherein the treatment that can be carried out by the implanted device isinitiated immediately after detecting MI/I.
 85. A method as in claim 83,wherein the treatment that can be carried out by the implanted device isinitiated within one hour after detecting MI/I.
 86. A method as in claim81, wherein the device includes a plurality of leads and positioning theleads at one or more positions selected from the group of intracavitary,epicardial, thoracic, and subcutaneous positions in the subject andtherapy includes delivering a shock to the subject through at least oneof the leads.
 87. A method of manufacturing an implantable deviceelected from the group consisting of pacemakers, cardio-defibrillators,atrial defibrillators, ventrical defibrillators, cardiac assist devices,and drug infusion devices, the method including the steps ofincorporating circuitry for monitoring the occurrence of a MI/I in asubject and providing a signal indicating the occurrence of a MI/I. 88.A method as in claim 87, further comprising delivering the signal to adevice external to the implantable device.
 89. A method as in claim 87,further comprising alerting the subject of the occurrence of a MI/I. 90.A method as in claim 76, wherein detecting MI/I comprises detecting MI/Iselected from the group consisting of transient MI/I, permanent MI/I,and recurrent MI/I.
 91. A method as in claim 76, wherein detecting MI/Icomprises detecting MI/I following an event selected from the groupconsisting of cardiac arrest, cardioversion, and defibrillation.
 92. Amethod as in claim 76, wherein detecting MI/I comprises detecting MI/Ifollowing an event selected from the group consisting of drug infusionand angioplasty therapy.
 93. A method as in claim 76, wherein detectingMI/I comprises detecting MI/I in the presence of an event selected fromthe group of arrhythmia and normal sinus rhythm.
 94. An apparatus fordetecting MI/I in a subject, comprising: an implantable container; atleast one lead adapted for insertion into the heart; at least one sensoradapted for insertion into the heart; and a microprocessor in thecontainer to analyze data from the at least one sensor.
 95. An apparatusas in claim 94, further comprising circuitry to transmit a signal fromthe sensor to the microprocessor.
 96. An apparatus as in claim 95,further comprising means to alert the subject after detecting MI/I. 97.An apparatus as in claim 95, further comprising means to communicatewith at least one device external to the subject.
 98. An apparatus as inclaim 94, further comprising means for initiating therapy afterdetecting MI/I.
 99. An apparatus as in claim 95, further comprising asupply of at least one drug adapted for insertion into the body, whereinthe supply is released upon receiving a signal from the microprocessor.100. An apparatus as in claim 94, wherein the container comprises a canthat is adapted to fit inside of the subject's heart.
 101. An apparatusas in claim 94, wherein the container comprises a can comprising theshape of an implanted device selected from the group consisting of apacemaker, a cardioverter, a defibrillator, a cardiac assist device, andan infusion pump.
 102. An apparatus as in claim 94, wherein thecontainer comprises a can having a triangular shape.
 103. An apparatusas in claim 94, wherein the container comprises a can shaped in the formof a pouch adapted to surround a portion of a heart.
 104. An apparatusas in claim 94, wherein the container comprises a can shaped to includethree orthogonal locations for mounting electrodes.
 105. An apparatus asin claim 94, wherein the container comprises a can shaped to includelocations to permit Einthoven triangle electrode placement.
 106. Anapparatus as in claim 94, wherein the container comprises a can, whereinat least one sensor is mounted on the can. 107 An apparatus as in claim94, further comprising an electrode, wherein the sensor is attached tothe lead through the electrode.
 108. An apparatus as in claim 94,wherein the sensor includes an electrode coupled to the lead.
 109. Anapparatus as in claim 108, comprising a plurality of electrodes adaptedfor insertion into the heart in a variety of locations.
 110. Anapparatus as in claim 94, wherein the lead is configured to transmitelectrogram signals from at least two locations selected from the groupconsisting of atrial heart cavity locations, ventricular heart cavitylocations, epicardial heart locations, thoracic locations surrounding aheart, and subcutaneous locations adjacent to a heart.
 111. An apparatusas in claim 94, wherein at least one lead includes a plurality ofsensors coupled thereto.
 112. An apparatus as in claim 94, wherein atleast one lead includes a plurality of electrically conductive sensorelements thereon.
 113. An apparatus as in claim 94, wherein at least onelead includes multiple unipolar elements.
 114. An apparatus as in claim94, wherein at least one lead includes multiple bipolar elements. 115.An apparatus as in claim 94, wherein the container acts as a referencefor electrical common.
 116. An apparatus as in claim 94, wherein atleast one sensor is mounted on the container and at least one sensor ismounted to a lead a distance away from the container.
 117. Animplantable apparatus for monitoring a subject for MI/I comprising: ahermetically sealed container; circuitry disposed within the container;an analog to digital converter disposed within the container; a logicdevice disposed within the container; and a feed-through interfacebetween at least one lead extending from the container and thecircuitry.
 118. An apparatus as in claim 117, wherein the logic devicecomprises a microprocessor.
 119. An apparatus as in claim 117, furthercomprising at least one amplifier disposed within the container.
 120. Anapparatus as in claim 119, further comprising at least one filterdisposed within the container.
 121. An apparatus as in claim 117,further comprising at least one sensor to recognize a MI/I condition,the sensor being coupled to a lead.
 122. An apparatus as in claim 121,wherein the sensor comprises a sensor selected from the group consistingof a blood pO₂ sensor, a blood pH sensor, a blood lactate sensor, ablood temperature sensor, and a tissue impedance sensor.
 123. Anapparatus as in claim 117, wherein the monitoring for MI/I includesseparating normal from ischemic electrogram signals by means to performelectrogram waveform analysis for temporal features including peaks andinflections.
 124. An apparatus as in claim 117, wherein the monitoringfor MI/I includes separating normal from ischemic electrogram signals bymeans to perform electrogram waveform analysis using time-domain signalanalysis.
 125. An apparatus as in claim 117, wherein the monitoring forMI/I includes separating normal from ischemic electrogram signals bymeans to perform electrogram waveform analysis using frequency domainmethods.
 126. An apparatus as in claim 117, wherein the monitoring forMI/I includes separating normal from ischemic electrogram signals bymeans to perform electrogram waveform analysis using combined time andfrequency analysis.
 127. An apparatus as in claim 117, wherein themonitoring for MI/I includes separating normal from ischemic electrogramsignals by means to analyze changes in depolarization andrepolarization.
 128. An apparatus as in claim 117, wherein themonitoring for MI/I includes means for detecting a MI/I signal bydetermining its temporal features synchronous to the Q, R, S, and Twaves in an electrogram signal.
 129. An apparatus for determining thelocation of a myocardial ischemic event comprising an implantable deviceincluding a plurality of sensors adapted to be positioned in variouslocations in and on the heart, the device further including means foranalyzing the changes in electrogram signals received from the sensors.130. An apparatus as in claim 129, further comprising means fordetermining the location using dipole projection.
 131. An apparatus forrecording and storing MI/I information, comprising: an implantabledevice comprising: means for digitizing electrogram signals means forstoring the signals; means for recording the digitized electrogramsignals in memory; means for recovering the digitized electrogramsignals in memory; and means for transmitting a signal from theapparatus to an external source.
 132. An apparatus as in claim 131,further comprising an external source and means for receiving thetransmitted signal by the external source.
 133. An apparatus fordetecting MI/I in a subject, comprising: means for detecting MI/I; andmeans for generating a signal to alert the subject about the MI/I;wherein the means for detecting and the means for generating the signalare implanted in the subject.
 134. An apparatus for detecting MI/I in asubject, comprising: an implantable container; at least one lead adaptedfor insertion into the heart and electrically connected to circuitry inthe container; at least one sensor coupled to the at least one lead andadapted for insertion into the heart; a microprocessor in the containerto analyze data from the at least one sensor; and a transmitter.
 135. Anapparatus as in claim 134, wherein the transmitter comprises a deviceselected from the group consisting of an RF transmitter, an electricaltransmitter, and an electromagnetic transmitter.
 136. An apparatus as inclaim 134, wherein the transmitter comprises means to transmit a signalto the subject.
 137. An apparatus as in claim 136, wherein thetransmitter comprises means to transmit a signal to a device externalfrom the subject.
 138. An implantable apparatus for detecting andtreating MI/I in a subject, comprising: a container; at least one leadadapted for insertion in the user and electrically connected tocircuitry in the container; at least one sensor coupled to the at leastone lead; a logic device in the container to analyze data from the atleast one sensor; and a supply of at least one drug to treat MI/I. 139.An apparatus as in claim 138, wherein the supply comprises at least onedrug selected from the group consisting of bicarbonate, epinephrine,heparin, TPA, streptokinase, and beta blockers.
 140. An apparatus as inclaim 138, wherein at least a portion of the supply is housed in apolymeric matrix.
 141. An apparatus as in claim 139, wherein at least aportion of the supply is housed in a structure selected from the groupconsisting of a lead, an indwelling catheter, and tubing.
 142. Animplantable apparatus for detecting and treating MI/I in a subject,comprising: a container; a plurality of leads electrically connected tocircuitry in the container; a plurality of sensors coupled to theplurality of leads; a logic device in the container to analyze data fromthe plurality of leads; and means for treating the subject in responseto a determination that a MI/I has occurred.
 143. An apparatus as inclaim 142, wherein the means comprises means for delivering an electricshock to the subject.
 144. An apparatus as in claim 142, wherein themeans comprises means for controlling the delivery of one or more drugsto the user.
 145. An implantable apparatus for detecting and treatingMI/I in a subject, comprising: a plurality of sensors coupled to theplurality of leads, wherein at least one sensor is adapted for placementin or on the subject's heart; and a logic device to analyze data fromthe plurality of leads and determine if a MI/I has occurred.
 146. Anapparatus as in claim 145, further comprising a structure selected fromthe group consisting of a pacemaker, a cardioverter-defibrillator, anatrial defibrillator, a cardiac assist device, and a drug infusiondevice.
 147. An apparatus as in claim 134, wherein the implantablecontainer is adapted to fit within a heart cavity.
 148. An apparatus asin claim 134, wherein the implantable container is adapted to fittransvenously within a subject.